Conventional solar water heater systems are usually comprised of a solar panel connected by pipes to a hot water storage tank for thermosyphonic circulation of water. The system has been proven to be simple to use and to be an impressive energy-saving device. In cold, cloudy weather, hot water is obtained by actuation of an electric heating element contained in the storage tank.
The main drawbacks of existing systems concern maintenance. The present arrangement is that at the base of the cylindrical insulated storage tank there is an opening of about 20 cm diameter which is closed by a flange held tightly by nuts, which in turn, are engaged with a set of firmly welded-on threaded studs. In the common vertical-axis tank, the flange is disposed at the bottom face of the tank. The flange supports the electric heater element and a thermostat, both of which project into the water storage tank. The joint between the flange and the opening is a well-known region for the start of corrosion and eventual leakage. Maintenance activities such as cleaning of built-up scale and accessing the electrical connections in the available restricted space are difficult, and are all the more difficult for changing the flange and/or thermostat, since before any action is possible, all the contents of the storage tank must be drained out, thereby wasting between tens and hundreds of liters of water. Thus, a simple maintenance task such as removing scale, replacing a burnt-out electric element, etc., requires much time and effort.
To ensure the availability of hot water in a plumbing system, several devices have been patented. In U.S. Pat. No. 5,072,717, to Laing et al, there is disclosed a priming device upstream from a hot water tap for storing a small amount of water at a continuously maintained temperature. When the tap is opened, the stored water is delivered out of the faucet, while the cold water that has been stationary in the hot water pipe, is fed into the priming device. Similarly, U.S. Pat. No. 5,944,221 to Laing et al, teaches a system of a water heater, a tank and a pump for pre-storing an amount of hot water that is delivered upon demand through a hot water faucet while the equal amount of cold water is pumped into the tank.
The above systems do provide hot water on demand until the water from the hot water pipe arrives at a necessary temperature, however, these devices do not render themselves useful for service in solar-radiation water heating systems, since the devices are not capable of continuous operation required to compensate for the cooling effects of wintry, cloudy weather on the water in the hot water storage tank. Moreover, the system is greatly encumbered by the incorporation of valves and pumps.
To keep large amounts of hot water available to consumers, U.S. Patent Application No. 2004/0237908 teaches a system composed of a water heater tank and a supplemental tank. The supplemental tank is used to store hot water available for immediate delivery through a hot water faucet. The system, however, fails to be applicable in the solar-radiation water heating systems, because the system fails to address the drawbacks of the solar panels.
In U.S. Pat. No. 6,119,682 to Hazan, there is described and claimed a water heater and storage device containing a solar panel and a tank, which further has a heat exchanger piping circuit to facilitate the transfer of heat from the water stored in the tank to cold line-pressure water. An electrical water heating element is disposed in the general proximity to the heat exchanger. The system disclosed in this patent aims to provide a more economical heating of cold water. The design of the system renders the water tank filled unnecessarily with complicated pipe-work of the heat exchanger disposed too close to the heating element
In contradistinction to the above prior art systems, the present invention achieves higher energy savings and efficiency by means of an external water heater, and provides for an extremely simple, easy to service system.
It is known in practice that heating elements working continuously in non-distilled water become coated with a deleterious layer of insoluble mineral deposits. In common water heater construction, all the more so in the solar panel systems, to change a thermostat or the heating element calls for work performed in awkward, obstructed spaces, and also calls for draining large amounts of water from the water heater being serviced.